U.S. patent application number 11/253889 was filed with the patent office on 2007-02-01 for method of creating ophthalmic lenses using modulated energy.
Invention is credited to Rafael Victor Andino, Angelika Maria Domschke, Joseph Michael Lindacher, Courtney Flem Morgan.
Application Number | 20070023942 11/253889 |
Document ID | / |
Family ID | 34956103 |
Filed Date | 2007-02-01 |
United States Patent
Application |
20070023942 |
Kind Code |
A1 |
Andino; Rafael Victor ; et
al. |
February 1, 2007 |
Method of creating ophthalmic lenses using modulated energy
Abstract
This invention is related to lenses and the associated processes
used to manufacture lenses. In particular, the present invention is
related to a process for designing and creating bifocal,
multifocal, and single vision ophthalmic lenses by modulating an
energy source.
Inventors: |
Andino; Rafael Victor;
(Lawrenceville, GA) ; Domschke; Angelika Maria;
(Duluth, GA) ; Lindacher; Joseph Michael;
(Suwanee, GA) ; Morgan; Courtney Flem;
(Alpharetta, GA) |
Correspondence
Address: |
NOVARTIS;CORPORATE INTELLECTUAL PROPERTY
ONE HEALTH PLAZA 104/3
EAST HANOVER
NJ
07936-1080
US
|
Family ID: |
34956103 |
Appl. No.: |
11/253889 |
Filed: |
October 19, 2005 |
Current U.S.
Class: |
264/1.32 ;
264/1.36; 264/1.38; 264/401 |
Current CPC
Class: |
B33Y 80/00 20141201;
B29C 35/0805 20130101; B29K 2105/243 20130101; B29D 11/00134
20130101; B29D 11/00355 20130101; B29L 2011/0016 20130101; B29C
35/0894 20130101; B29D 11/00442 20130101; B29L 2011/0033 20130101;
B29C 2035/0827 20130101 |
Class at
Publication: |
264/001.32 ;
264/001.36; 264/001.38; 264/401 |
International
Class: |
B29D 11/00 20060101
B29D011/00; B29C 35/08 20070101 B29C035/08; B29C 41/02 20070101
B29C041/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 29, 2005 |
EP |
EP2005/008270 |
Claims
1. A method for making an ophthalmic lens comprising Providing a
fluid optical material; Providing a mold; Injecting said fluid
optical material into said mold; Exposing said mold and fluid
optical material to an energy source; and modulating said energy
source to create at least one index of refraction in the optical
zone of the lens.
2. The method of claim 1, wherein said energy source is selected
from the group consisting of UV light.
3. The method of claim 1 and wherein said modulating step source
further comprises varying light intensity according to an
illumination scheme.
4. The method of claim 3, wherein said variation is accomplished by
creating a gray-scale mask.
5. The method of claim 4, wherein said gray scale mask is created
using stereo lithography.
6. The method of claim 4 wherein said gray scale mask is created by
a computer-generated hologram.
7. The method of claim 4 wherein said gray scale mask masks said
energy source in an illumination scheme, wherein said scheme
corresponds to a desired lens geometry.
8. The method of claim 7, wherein said desired lens geometry has
more than one optical zone.
9. The method of claim 1, wherein said exposing step further
comprises curing said fluid optical material into a lens.
10. The method of claim claim 1 wherein said ophthalmic lens is
selected from the group consisting of: a bifocal lens, a multifocal
lens, a toric lens, a customized lens and a single vision lens.
11. The method of claim 1, wherein said ophthalmic lens is designed
to correct one or more of the following defects: myopia,
hypermetropia, presbyopia, defocus, and astigmatism.
12. The method of claim 1, wherein said fluid optical material
comprises a prepolymer and a photoinitiator.
13. The method of claim 12, wherein said fluid optical material
further comprises a sensitizer.
14. The method of claims 12, wherein said fluid optical material
comprises an additive.
15. The method of claim 12, wherein said fluid optical material
comprises NaCl.
16. The method of claim 3, wherein said varying light intensity
further comprises providing a uniform light source in optical
connection with a DMD.
17. The method of claim 16 wherein said DMD is in optical
connection with said fluid optical material.
18. The method of claim 17, wherein one or more MEMS devices drives
one or more DMDs.
19. The method of claim 3, wherein said illumination scheme
corresponds to a desired lens geometry.
Description
[0001] This invention is related to ophthalmic lenses and the
associated processes used to manufacture ophthalmic lenses. In
particular, the present invention is related to a process for
designing and creating bifocal, multifocal, and single vision
ophthalmic lenses by modulating an energy source.
BACKGROUND
[0002] Contact lenses are widely used for correcting many different
types of vision deficiencies. These include defects such as
near-sightedness and far-sightedness (myopia and hypermetropia,
respectively), astigmatism, and defects in near range vision
usually associated with aging (presbyopia). Each type of defect
requires a specific correction and coordinating manufacturing
process or processes.
[0003] Astigmatism occurs because the refractive error in an eye is
dependent upon spatial distribution of the optical error.
Astigmatism is typically caused by one or more refractive surfaces,
most commonly the anterior cornea, having a toroidal shape.
Astigmatism can be corrected with an astigmatic ophthalmic lens,
which usually has one spherical surface and one toroidal
(cylindrical) surface.
[0004] Presbyopia occurs as a person ages because the lens of the
eye loses its elasticity, eventually resulting in loss of the
ability to focus at near distances. To compensate for presbyopia,
ophthalmic lenses are required to be more positively powered or
less negatively powered than the distance correction. Some
presbyopic persons have both near vision and distance vision
defects, requiring simultaneous or alternating vision lenses to
properly correct their vision.
[0005] Simultaneous vision lenses refer to the class of bifocal or
multifocal ophthalmic lenses in which optical power for distance
vision and near vision are positioned simultaneously within the
pupil area of a user's eye. They are generally composed of two or
more concentric annular zones which alternately provide the
distance and near power, or a multifocal zone having an aspheric
surface which provides a continuous gradient of optical power over
a selected range of powers.
[0006] Alternating vision refers to the class of segmented
(translating) bifocal ophthalmic lenses in which the lens is
divided into two or more optical zones. Typically the superior
(upper) zone is for distance vision correction, whereas the lower
zone is for near vision correction. The distance portion subtends
the pupil of the eye in primary gaze. In downward gaze the add
power or near portion (lower zone) of the lens subtends the pupil.
Lenses for this type of defect can be created, for example, by
molding, casting or lathing processes.
[0007] Additionally, some lens-wearers may need more than one
correction. For example, a person with presbyopia may also have an
astigmatism vision error. Those presbyopes may require ophthalmic
lenses capable of correcting both astigmatism and presbyopia.
Lenses that incorporate corrections for both types of defects
usually combine one or more manufacturing processes or entail a
lengthier single process.
[0008] Lenses that are designed to correct the above-referenced
defects may be created through molding, casting or lathe-cutting.
For example, contact lenses that are manufactured in large numbers
are typically produced by a mold process. In those processes, the
lenses are manufactured between two molds without subsequent
machining of the surfaces or edges. Such mold processes are
described, for example in U.S. Pat. No. 6,113,817, which is
expressly incorporated by reference as if fully set forth herein.
As such, the geometry of the lens is determined by the geometry of
the mold. In a typical molding system, lenses are cycled through a
series of stations on a semi-continuous basis. The cyclic portion
of lens production generally involves dispensing a liquid
crosslinkable and/or polymerizable material into a female mold
half, mating a male mold half to the female mold half, irradiating
to crosslink and/or polymerize, separating the mold halves and
removing the lens, packaging the lens, cleaning the mold halves and
returning the mold halves to the dispensing position. The
polymerization of the material is determined by the application
time, position, and amount of UV light applied. Similar to mold
geometry, the UV radiation is generally altered for different types
of lenses. As such, producing different types of lenses and powers
may not be efficient.
[0009] For defocus or correction lenses there is typically one
design parameter, which is the spherical power. Each different lens
power requires at least one set of molding tools and/or molds.
Hence, to provide a lens line serving most optical powers, a
moderate number of molding tools and/or molds are needed. For toric
lenses, at least three parameters must be considered: spherical
power, cylindrical power, and the orientation of the cylindrical
power. The permutations of all of these powers produce a large,
almost unmanageable number of unique lens stock keeping units
(SKUs), and an even larger number of molding tools and molds.
Similarly, for multifocal lenses, a huge number of molding tools
and molds is required.
[0010] Additionally, some persons require made-to-order (MTO) or
customized lenses. Each customized lens required its own molding
tools and molds. As such, the cost of MTO lenses is very high and
may even be cost-prohibitive.
SUMMARY OF THE INVENTION
[0011] The present invention seeks to solve the problems listed
herein by reducing the number of molding tools and molds to produce
a large number of lenses of varying parameters. The present
invention also seeks to provide a means for cost-effective
production of MTO or customized lenses.
[0012] In accomplishing the foregoing, there is provided, in
accordance with one aspect of the present invention, a method for
designing a lens with multiple zones within the material bulk.
[0013] The invention, in another aspect, provides a method for
creating a lens with one or more refractive indices in the optical
zone of a lens that are spatially distributed throughout the
optical portion of the lens to correspond with vision correction
needs.
[0014] The invention, in a further aspect, provides a method of
modulating or attenuating UV light to achieve differential curing
of bulk material.
[0015] The invention, in a further aspect, provides methods for the
design and manufature of toric lenses of varying power.
[0016] The invention, in another further aspect, provides methods
for the design and manufacture of at least two optical zones in any
configuration.
[0017] The invention, in still another aspect, provides methods for
the design and manufacture of lenses with holographic or grating
patterns.
[0018] The invention also provides a method for making an
ophthalmic lens by providing fluid optical material, providing a
mold, injecting the fluid optical material into the mold, and
exposing both the mold and the fluid optical material to a
modulated energy source to create at least one index of refraction
in the optical zone of a lens. In this method, the energy source
may be UV radiation. In another embodiment, modulating the energy
source may be accomplished by varying the light intensity according
to an illumination scheme. In a related embodiment, the light
intensity variation may be accomplished by either a gray scale
mask, using a uniform light source in optical connection with a
digital mirror device (DMD), or by other similar spaital light
modulators, including dynammic programmable masks. In a method in
which a gray scale mask is used, the gray scale mask may be created
by stereo lithography or by a computer-generated hologram. In a
method in which a DMD is used, the DMD is preferably in optical
connection with the uniform light source and the fluid optical
material.
[0019] In another embodiment of the invention, the illumination
scheme corresponds to a lens geometry. In another embodiment, the
lens geometry may have more than one optical zone. In still another
embodiment of the present invention the ophthalmic lens may be a
toric lens, a bifocal lens, a multifocal lens, a customized lens or
a single vision lens. In another embodiment the lens is designed to
correct myopia, hypermetropia, proesbyopia, astigmatism, and/or
defocus.
[0020] These and other aspects of the invention will become
apparent from the following description of the preferred
embodiments taken in conjunction with the following drawings. As
would be obvious to one skilled in the art, many variations and
modifications of the invention may be effected without departing
from the spirit and scope of the novel concepts of the
disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1A illustrates a plan view of one embodiment of a mold
carrier in an open position.
[0022] FIG. 1B shows an end sectional view of the FIG. 1A mold
carrier in an open position.
[0023] FIG. 1C shows an end sectional view of the FIG. 1A mold
carrier in a closed position.
[0024] FIG. 2 depicts a screen shot of a lens design program.
[0025] FIG. 3A depicts a plan view of a DMD according to an
experimental setup of the present invention.
[0026] FIG. 3B depicts a plan view of a DMD according to an
experimental setup of the present invention.
[0027] FIG. 3C depicts a frontal view of a DMD according to an
experimental setup of the present invention.
DETAILED DESCRIPTION OF THE EMBODIMENT
[0028] Reference now will be made in detail to the embodiments of
the invention. It will be apparent to those skilled in the art that
various modifications and variations can be made in the present
invention without departing from the scope or spirit of the
invention. For instance, features illustrated or described as part
of one embodiment can be used in conjunction with another
embodiment to yield a still further embodiment. Thus, it is
intended that the present invention cover such modifications and
variations as come within the scope of the appended claims and
their equivalents. Other objects, features and aspects of the
present invention are disclosed in or are obvious from the
following detailed description. It is to be understood by one of
ordinary skill in the art that the present discussion is a
description of exemplary embodiments only, and is not intended as
limiting the broader aspects of the present invention. All patents
and patent applications disclosed herein are expressly incorporated
by reference in their entirety.
[0029] Unless defined otherwise, all technical and scientific terms
used herein have the same meaning as commonly understood by one of
ordinary skill in the art to which this invention belongs.
Generally, the nomenclature used herein and the manufacturing
procedures are well known and commonly employed in the art.
Conventional methods are used for these procedures, such as those
provided in the art and various general references. Where a term is
provided in the singular, the inventors also contemplate the plural
of that term.
[0030] An "ophthalmic device," as used herein, refers to a contact
lens (hard or soft), a corneal onlay, implantable ophthalmic
devices used in, on or about the eye or ocular vicinity. The term
"contact lens" employed herein in a broad sense and is intended to
encompass any hard or soft lens used on the eye or ocular vicinity
for vision correction, diagnosis, sample collection, drug delivery,
wound healing, cosmetic appearance (e.g., eye color modification),
or other ophthalmic applications.
[0031] A "hydrogel material" refers to a polymeric material which
can absorb at least 10 percent by weight of water when it is fully
hydrated. Generally, a hydrogel material is obtained by
polymerization or copolymerization of at least one hydrophilic
monomer in the presence of or in the absence of additional monomers
and/or macromers. Exemplary hydrogels include, but are not limited
to, poly(vinyl alcohol) (PVA), modified polyvinylalcohol (e.g., as
nelfilcon A), poly(hydroxyethyl methacrylate), poly(vinyl
pyrrolidone), PVAs with polycarboxylic acids (e.g., carbopol),
polyethylene glycol, polyacrylamide, polymethacrylamide,
silicone-containing hydrogels, polyurethane, polyurea, and the
like. A hydrogel can be prepared according to any methods known to
a person skilled in the art.
[0032] A "crosslinkable and/or polymerizable material" refers to a
material which can be polymerized and/or crosslinked by actinic
radiation to obtain crosslinked and/or polymerized material which
are biocompatible. Examples of actinic radiation are UV
irradiation, ionized radiation (e.g. gamma ray or X-ray
irradiation), microwave irradiation, and the like.
[0033] "Polymer" means a material formed by polymerizing one or
more monomers.
[0034] A "prepolymer" refers to a starting polymer which can be
polymerized and/or crosslinked upon actinic radiation to obtain a
crosslinked polymer having a molecular weight much higher than the
starting polymer.
[0035] The term "fluid" as used herein indicates that a material is
capable of flowing like a liquid.
[0036] "Fluid optical material" as used herein means a polymer, a
prepolymer, a corsslinkable and/or polymerizable material, and/or a
hydrogel material that is capable of flowing like a liquid.
[0037] The present invention is generally related to the
manufacture and design of contact lenses. In one aspect, the
present invention provides a method to produce a lens optical zone
with a desired power by modulating an energy source to create
varying light intensity according to an illumination scheme. The
varied light intensity differentially cures the fluid optical
material to create a spatial distribution of refractive indices in
the optical zone of a lens within the cured lens. The intensity of
the energy source, such as UV light, for example, is varied to
manipulate the optical wavefront. The optical wavefront may be
manipulated according to a specified pattern, such as a Zernike
polynomial basis set or a presbyopic aberration pattern. The
optical wavefront may be dervied from the aberrometry data, corneal
topography data or calculated as with a presbyopic correction
wavefront.
[0038] As will be readily appreciated by those of skill in the art,
many different types of lenses are possible with the present
invention. Contact lenses of the invention can be either hard or
soft lenses. A contact lens of the invention can be a toric,
multifocal, toric multifocal contact lens, customized contact
lenses, or the like. Contact lenses of the present invention may
also correct more than one type of defect, such as, for example,
presbyopia and astigmatism. According to the present invention,
each of these types of lenses may be created by an illumination
scheme or energy modulation.
[0039] Soft contact lenses of the invention are preferably made
from a fluid optical material, such as a silicon or
fluorine-containing hydrogel or HEMA with material properties that
allow modulation of a refractive index. It will be understood that
any fluid optical material can be used in the production of a
contact lens of the invention. Preferred materials and formulations
suitable for this application preferably consist of pure or
specifically modified hydrogels, preferably polyvinylalcohols (PVA)
containing radiation activated crosslinkable functional groups that
may be photoinitiated when exposed to a particular wavelength.
[0040] Ophthalmic lenses may be produced by double-sided molding
(DSM) processes. These processes typically involve dispensing a
liquid monomer into a female mold half, mating a male mold half to
the female, and applying ultraviolet radiation to polymerize the
monomers. Such molds may be injection molded or produced in any
other feasible way known in the art. The female mold half may have
a molding surface that defines the anterior (front) surface of a
contact lens. The male mold half may have a molding surface that
defines the posterior (back) surface of the lens. The polymerized
lens removed from the molds in a DSM process does not usually
require surface polishing, but subsequent extraction of unreacted
monomer or solvent is commonly required.
[0041] An improvement of the DSM process is described in U.S. Pat.
No. 6,113,817. This improvement may be semi-cyclic and preferably
includes the steps of (a) dispensing crosslinkable and/or
polymerizable material into a female mold half, (b) mating a male
mold half to a female mold half to create a lens cavity; (c)
applying radiation to crosslink and/or polymerize the crosslinkable
and/or polymerizable material to form a lens; (d) separating the
male mold half from the female mold half; (e) washing the mold
halves and lens to remove unreacted crosslinkable and/or
polymerizable material; (f) ensuring the lens is adjacent a
selected mold half (e.g., the female mold half); (g) centering the
lens within the selected mold half; (h) grasping the lens (e.g., in
a central area) to remove the lens from the mold half; (i) at least
partially drying the lens to remove surface water which may impair
inspection of the lens; (j) inspecting the lens; (k) depositing an
acceptable lens into packaging; (l) cleaning the male and female
mold halves; and (m) indexing the male and female mold halves to a
position for dispensing crosslinkable and/or polymerizable
material. This semi-continuous, partially cyclic molding process
reuses or recycles the mold halves used to retain the fluid optical
material and give the lens its shape.
[0042] The semi-continuous, partially cyclic molding process may be
operated with a single mold cycling through the process. However,
in a preferred embodiment, the process utilizes a plurality of
molds arranged and aligned in a molding carrier in order to improve
process efficiency. For example, FIG. 1A illustrates a plan view of
one embodiment of a molding carrier 20 having an array of ten
complete molds. Molding carrier 20 includes an array of ten female
mold halves 22 removably positioned in a first housing 24. Molding
carrier 20 further includes an array of ten male mold halves 26
removably positioned in a second housing 28. First housing 24 is
affixed to second housing 28 by a pivoting means 30, which allows
second housing 28 to articulate towards first housing 24 in order
to releasably mate the male and female mold halves. Thus, first
housing 24 is hingedly affixed to second housing 28.
[0043] In operation, a fluid optical material (or a solution or
dispersion thereof) is dispensed into female mold halves 22. Male
mold halves 26 are mated with female mold halves 22 by rotating and
linearly moving second housing 28, as showing by the arrow in FIG.
1B to create a mold cavity. Molding carrier 20 is shown in a closed
position (i.e., molding position) in FIG. 1C. In FIG. 1C, all ten
pairs of mold halves are mated, thereby defining ten molding
cavities 32 in which a lens may be formed.
[0044] The mold halves may be formed from a number of materials, at
least one of which transmits the desired radiation for crosslinking
and/or polymerization, preferably in the ultraviolet range. One
preferred material which may be used for reusable molds is quartz.
Preferably only one mold half transmits sufficient radiation while
the other does not. Quartz offers substantial advantages in
durability, thereby allowing the molds to be reused a remarkable
number of times without affecting product quality. However, quartz
molds may be quite expensive. Alternatively, the mold halves may be
molded from a polymeric material, at least one of which transmits
the desired radiation. Examples of suitable mold materials include
PMMA, polycarbonate, Zenex, Zenor, OPI Resin by Hitachi,
TOPAS.RTM., polystyrene, polypropylene and poly(acrylonitriles)
such as BAREX.
[0045] In a preferred embodiment, the mold halves of at least one
of the set of male mold halves or the set of female mold halves
includes a peripheral region which blocks light (especially UV
light) during polymerizing and/or crosslinking. Use of such a light
blocking periphery enables a precise definition of the edge of the
lenses which are formed. This region may be produced by depositing
a metallic or UV absorbing coating in the region outside the lens
forming surfaces of the mold halves.
[0046] The design of the lens involves the creation of a zone or
multiple zones within the material bulk within the lens geometry.
The lens geometry may contain a single refractive index or multiple
refractive indices in the optical zone of a lens, depending upon
the type of correction needed. In general, most current lenses have
a substantially uniform index of refraction.
[0047] The present invention seeks to produce a lens with a spatial
distribution of refractive index/indices. Additionally, the lens
may comprise a zone with a varying index gradient. The index or
indices of refraction, in combination with or in lieu of a surface
geometry optical design preferably create the optical power of the
lens. The location of these zones is determined by the desired
optical design of the lens. The zone or zones with a constant or
varying index gradient may be used to produce a single vision lens,
a toric lens, a bifocal lens, a multifocal lens or any combination
thereof.
[0048] The power of the lens is a function of the curvature of the
anterior and posterior surfaces. Specifically, the power of the
lens is measured in diopters, which is the reciprocal of the focal
length of the lens: 1 f = ( n - 1 ) .times. ( 1 r 1 - 1 r 2 ) + ( n
- 1 ) 2 n .times. t c r 1 .times. r 2 ##EQU1## where [0049]
n=refractive index [0050] t.sub.c=center thickness [0051]
r.sub.1=radius of curvature of first surface (positive if center or
curvature is to right) [0052] r.sub.2=radius of curvature of second
surface (negative if center of curvature is to left).
[0053] Typically, the surface of a lens is changed to alter the
focal length, which corrects vision; however, the present invention
seeks to correct vision by altering the refractive index.
[0054] The most commonly used optical surface or shape is a
spherical surface. The sphere is centered on the optical axis. The
"sag" or z-coordinate of a standard spherical surface is given by:
Standard Spherical Surface z = cr 2 1 + 1 - ( 1 + k ) .times. c 2
.times. r 2 ##EQU2## where [0055] c=curvature (reciprocal of the
radius) [0056] r=radial coordinate in lens units [0057] k=conic
constant; the conic constant is less than -1 for hyperbolas,-1 for
parabolas, between -1 and 0 for ellipses, 0 for spheres, and
greater than 0 for oblate ellipsoids
[0058] A biconic surface best defines the lens surface or shape of
a toric lens. The "sag" or z-coordinate of a biconic surface is
given by: Biconic Surface z = c x .times. x 2 + c y .times. y 2 1 +
1 - ( 1 + k x ) .times. c x 2 .times. x 2 - ( 1 + k y ) .times. c y
2 .times. y 2 ##EQU3## where .times. .times. c x = 1 r x , c y = 1
r y , ##EQU3.2##
[0059] A reference index of refraction can be defined by the
following equation:
n.sub.ref=n.sub.0+n.sub.r2r.sup.2+n.sub.r4r.sup.4+n.sub.z1z+n.s-
ub.z2z.sup.2+n.sub.z3z.sup.3+n.sub.z4z.sup.4 where
r.sup.2=x.sup.2+y.sup.2
[0060] The reference index of refraction can be used to calculate
the reference wavelength. The refractive index at any other
wavelength can then be computed using the following general
expansion of the Sellmeier formula: n .function. ( .lamda. ) 2 = n
.function. ( .lamda. ref ) 2 + i = 1 3 .times. K i .function. (
.lamda. 2 - .lamda. ref 2 ) .lamda. 2 - L i , ##EQU4## where
K.sub.i and L.sub.i define the dispersion of the material. The
dispersion is a material property and is known in the art.
[0061] All of the preceding calculations are typically performed by
an optical design software program as described below once certain
parameters are entered by a user.
[0062] The lens design included in the present invention seeks to
cancel or correct optical aberrations and defocus. The two basic
methods for correcting defect/defocus involve designing a lens
surface profile or by changing the index or indices of refraction
by the cure. The present invention seeks to correct vision by
spatially distributing the index or indices of refraction in the
optical zone of a lens to compensate for defects. A lens design may
be pre-designed as a generic lens or can be specially designed for
a user.
[0063] In a specific embodiment in which an ophthalmic lens is
designed for the user, an ophthalmic wavefront sensor may be used
to measure the irregularities on the eye, such as for example, a
Shack-Hartmann wavefront sensor. Measurements of the wavefront
aberrations of the eye to a high degree of precision using an
improved Hartmann-Shack wavefront sensor are described in U.S. Pat.
No. 5,777,719, which is expressly incorporated by reference as if
fully set forth herein.
[0064] Starting at the retina, an ideal wavefront is generated,
which passes through the optical path of the eye. The wavefront
sensor illuminates the fovea with a narrow-beam light source,
typically a laser diode or an LED, and records the position of the
scattered light through a lenslet array. As the wavefront (the
optical wavefront of the electromagnetic wave from the optical
element) exits the eye, it contains a complete map of the eye's
aberrations for analysis by the sensor. The lenslet array breaks up
the nearly collimated beam into points on a digital camera,
typically a CCD or a CMOS imager. Once the wavefront is received by
the sensor, a complex series of analyses may be performed to
provide a more complete picture of the eye's optical path. The data
may then be fit to a Zernike basis set.
[0065] The essential data provided by a Hartmann-Shack wavefront
sensor that is modified to measure the human eye are the directions
of the optical rays emerging through the eye's pupil. The method of
deriving a mathematical expression for the wavefront from this
directional ray information is described in U.S. Pat. No.
5,777,719. First, the wavefront is expressed as a series of Zernike
polynomials with each term weighted initially by an unknown
coefficient. Next, partial derivatives (in x & y) are then
calculated from the Zernike series expansion. Then, these partial
derivative expressions respectively are set equal to the measured
wavefront slopes in the x and y directions obtained from the
wavefront sensor measurements. Finally, the method of least-squares
fitting of polynomial series to the experimental wavefront slope
data is employed which results in a matrix expression which, when
solved, yields the coefficients of the Zernike polynomials.
Consequently, the wavefront, expressed by the Zernike polynomial
series, may be completely and numerically determined numerically at
all points in the pupil plane. The least-squares fitting method is
discussed in chapter 9, Section 11 of "Mathematics of Physics and
Modern Engineering" by Sokolnikoff edheffer (McGraw-Hill, New York,
1958). The benefit of this analysis is that the wavefront can be
broken into independent mathematical components that represent
specific aberrations.
[0066] A table of the proposed OSA Standard (Optical Society of
America) Zernike Polynomials up to 7th order is displayed below
(More information on Zernike polynomials is available on
http:/color.eri.harvard.edu/standardization/standards_TOPS4.pdf).
TABLE-US-00001 Table of Zernike Polynomials in Polar Coordinates up
to 7.sup.th order (36 terms) j n m Z.sub.n.sup.m (.rho., .theta.) 0
0 0 1 1 1 -1 2 .rho. sin .theta. 2 1 1 2 .rho. cos .theta. 3 2 -2
{square root over (6)} .rho..sup.2 sin 2.theta. 4 2 0 {square root
over (3)} (2.rho..sup.2 - 1) 5 2 2 {square root over (6)}
.rho..sup.2 cos 2.theta. 6 3 -3 {square root over (8)} .rho..sup.3
sin 3.theta. 7 3 -1 {square root over (8)} (3.rho..sup.3 - 2.rho.)
sin .theta. 8 3 1 {square root over (8)} (3.rho..sup.3 - 2.rho.)
cos .theta. 9 3 3 {square root over (8)} .rho..sup.3 cos 3.theta.
10 4 -4 {square root over (10)} .rho..sup.4 sin 4.theta. 11 4 -2
{square root over (10)} (4.rho..sup.4 - 3.rho..sup.2) sin 2.theta.
12 4 0 {square root over (5)} (6.rho..sup.4 - 6.rho..sup.2 + 1) 13
4 2 {square root over (10)} (4.rho..sup.4 - 3.rho..sup.2) cos
2.theta. 14 4 4 {square root over (10)} .rho..sup.4 cos 4.theta. 15
5 -5 {square root over (12)} .rho..sup.5 sin 5.theta. 16 5 -3
{square root over (12)} (5.rho..sup.5 - 4.rho..sup.3) sin 3.theta.
17 5 -1 {square root over (12)} (10.rho..sup.5 - 12.rho..sup.3 +
3.rho.) sin .theta. 18 5 1 {square root over (12)} (10.rho..sup.5 -
12.rho..sup.3 + 3.rho.) cos .theta. 19 5 3 {square root over (12)}
(5.rho..sup.5 - 4.rho..sup.3) cos 3.theta. 20 5 5 {square root over
(12)} .rho..sup.5 cos 5.theta. 21 6 -6 {square root over (14)}
.rho..sup.6 sin 6.theta. 22 6 -4 {square root over (14)}
(6.rho..sup.6 - 5.rho..sup.4) sin 4.theta. 23 6 -2 {square root
over (14)} (15.rho..sup.6 - 20.rho..sup.4 + 6.rho..sup.2) sin
2.theta. 24 6 0 {square root over (7)} (20.rho..sup.6 -
30.rho..sup.4 + 12.rho..sup.2 - 1) 25 6 2 {square root over (14)}
(15.rho..sup.6 - 20.rho..sup.4 + 6.rho..sup.2) cos 2.theta. 26 6 4
{square root over (14)} (6.rho..sup.6 - 5.rho..sup.4) cos 4.theta.
27 6 6 {square root over (14)} .rho..sup.6 cos 6.theta. 28 7 -7 4
.rho..sup.7 sin 7.theta. 29 7 -5 4 (7.rho..sup.7 - 6.rho..sup.5)
sin 5.theta. 30 7 -3 4 (21.rho..sup.7 - 30.rho..sup.5 +
10.rho..sup.3) sin 3.theta. 31 7 -1 4 (35.rho..sup.7 -
60.rho..sup.5 + 30.rho..sup.3 - 4.rho.) sin .theta. 32 7 1 4
(35.rho..sup.7 - 60.rho..sup.5 + 30.rho..sup.3 - 4.rho.) cos
.theta. 33 7 3 4 (21.rho..sup.7 - 30.rho..sup.5 + 10.rho..sup.3)
cos 3.theta. 34 7 5 4 (7.rho..sup.7 - 6.rho..sup.5) cos 5.theta. 35
7 7 4 .rho..sup.7 cos 7.theta.
[0067] In an embodiment without astigmatism or that is not a MTO
lens, the power needed, and hence the required refractive index or
indices are known. Other parameters such as diameter and base curve
are also known. These types of lenses are designed to correct
defocus and are made in specific known diopters with specific known
geometries. Hence, minimal calculation is needed to determine the
illumination scheme because less indices of refraction may be
needed to correct defocus. In an embodiment in which a progressive
lens is needed for presbyopia, errors are accounted for by the
Zernike index and the progressive addition profile of the lens.
[0068] The material's .DELTA.n, is the difference in the resultant
index at the minimal required exposure and the resultant index at
the maximum allowed cure exposure. Curing the lens outside of
defined limits will result in under-cured or over-cured lenses. The
lens designs incorporate the .DELTA.n the calculations. A digital
mirror device (DMD)., which is optically linked, may act as a
localized curing modulator. In the preferred embodiment, the DMD
controls the index of refraction along the surface of the lens
(x,y) lateral plane while the "n-parameter" along the z-axis (into
the lens) remains constant.
[0069] As previously stated and as is well known to those skilled
in the art, lens design for a contact lens can be carried out by
using an optical design system and a mechanical CAD system. The
design of the optical model lens can be transformed by, for
example, a mechanical CAD system, into a set of mechanical lens
design that includes optical zones, non-optical zones and
non-optical features. Exemplary non-optical zones and features of a
contact lens include, but are not limited to bevel, lenticular, the
edge that joins the anterior and posterior surfaces of a contact
lens, orientation features, and the like. Exemplary orientation
features include, but are not limited to, a prism ballast or the
like that uses a varying thickness profile to control the lens
orientation, a faceted surface (e.g., ridge-off zone) in which
parts of the lens geometry are removed to control the lens
orientation, and ridge feature that orients the lens by interacting
with the eyelid. Preferably, when transforming the design of an
optimized optical model lens into a mechanical lens design, some
common features of a family of contact lenses can be incorporated.
Any known, suitable mechanical CAD system can be used in the
invention. Preferably, a mechanical CAD system capable of
representing precisely and mathematically high order surfaces is
used to design a contact lens. An example of such mechanical CAD
system is Pro/Engineer.
[0070] Preferably, the design of a contact lens may be translated
back and forth between the optical CAD and mechanical CAD systems
using a translation format which allows a receiving system, either
optical CAD or mechanical CAD, to construct NURBs (non uniform
rational B-splines) or Beizier surfaces of an intended design.
Exemplary translation formats include, but are not limited to, VDA
(Verband Der Automobilindustrie) and IGES (Initial Graphics
Exchange Specification). By using such translation formats, overall
surface of lenses can be in a continuous form that facilitates the
production of lenses having radially asymmetrical shapes. Beizier
and NURBs surface are particular advantageous for presbyopic design
because multiple zones can be blended, analyzed and optimized.
[0071] After the optical and mechanical design for a contact lens
is completed, a lens design is preferably in a neutral file format,
for example, such as IGES or VDA, or in a proprietary file format
(for example, a Pro/E file format).
[0072] After the known defects are fit into a Zernike or similar
mathematical representation, the mathematical representation is
converted into optical power. This conversion is accomplished
through use of an optical software program, as shown in FIG. 2,
such as ZEMAX by ZEMAX Development Corporation (San Diego, Calif.),
Code V by Optical Research Associates (ORA) (Pasadena, Calif.),
OSLO by Sinclair Optics (Fairport, N.Y.), and ASAP by Breault
Research Organization (Tucson, Ariz.). These programs use
mathematical formulas presented earlier, as well as others, to
calculate the lens design and the correction needed to effectively
cancel the defect. The user may electronically input the properties
of the eye such as shape, refraction, reflection, index, gradient
index, thermal, polarization, transmission, and diffraction, for
example. The software then models sequential and non-sequential
imaging and corrects the defects by determining what index or
indices of refraction are needed to make the focus over the pupil
uniform. This may, in effect, require different indices of
refraction over the lens. The software seeks to normalize the index
of refraction over the pupil to provide uniform focus over the
pupil. The necessary correction then becomes the appropriate lens
design.
[0073] After the necessary lens is designed, it is then
manufactured. As stated previously, changing the index or indices
of refraction via the cure process creates the spatial distribution
of the refractive indices that is needed to provide the proper lens
for a particular aberration. This is accomplished by energy
modulation during the cure process.
[0074] During the manufacturing process, the molding tool is
indexed to a stage in which a form of radiation is impinged upon
the molds, which allow substantially all of the radiation to
transmit there through, and contact the fluid optical material.
Preferred wavelengths of radiation are in the ultraviolet (UV)
range and may be dependant upon the wavelength needed to
photoactivate the fluid optical material. Preferably, the
wavelength will correspond to the excitation wavelength of a
photoinitiator. The appropriate intensity and exposure time needed
to effect a particular index of refraction in a particular material
is known by those of skill in the art.
[0075] The irradiation period is preferably less than about 5
minutes, more preferably less than about a minute and even more
preferably less than about 10 seconds. Irradiation may be
accomplished in one step or stage of the process, but this is not a
requirement because more than one stage of the process may be used
for irradiation. For example, if a uniform stage duration of about
4 seconds is selected for the process, but an irradiation time of
about 6 seconds is desired, two irradiation stages may be inserted
into the process to provide adequate irradiation. Additionally, a
pre-cure step may be used, or additional irradiation stages may be
used. For example, uniform radiation may be applied for a short
period of time to produce a uniform refractive index, such as, for
example, an index of refraction of about 1.4. This pre-cure may
them be followed by a second, non-uniform period of irradiation to
reach a desired index of refraction, such as about 1.5 for example,
as described below.
[0076] The required irradiation period is a function of the
intensity of applied radiation, the chosen prepolymer, and the
particular photoinitiator used. A preferred intensity of
ultraviolet radiation for poly(vinyl alcohol) prepolymers is about
1-5 milliwatts per square centimeter, more preferably about 2 to
about 3.5 mW/cm.sup.2, and even more preferably about 2.8 to 3.2
mW/cm.sup.2. A preferred wavelength of applied radiation is about
280 to about 380 nanometers, more preferably about 305 to about 350
nm. Other wavelengths may also be used for other fluid optical
materials and their photoactivation wavelengths.
[0077] In a preferred embodiment of the present invention, the
fluid optical material, such as a hydrogel, will cure to produce a
spatial distribution of refractive indices. This spatial
distribution is preferably created in a pattern equivalent to the
light intensity and illumination scheme. The difference in the
index of refraction is proportional to the irradiance distribution
and thus inversely proportional to the optical density (OD). The
greater the index of refraction of the material, the greater the
power difference in various optical zones of the lens. As stated
previously, to provide vision correction, the index of refraction
over the pupil must be uniform. By changing the refractive index of
the lens in specific known areas of the lens to compensate for
known deficiencies found in the uncorrected eye, the index of
refraction can be normalized.
[0078] In one embodiment of the present invention, modulating the
energy source is accomplished through use of a gray scale mask. In
an embodiment using a gray scale mask, the mask has a varying OD
that controls the intensity of the UV light or other energy source
into the mold, forming different indices of refraction or index of
refraction gradients. In an embodiment using a gray scale mask, the
mask may be made using stereo lithographic techniques allowing a
high degree of precision within the mask design. The design of the
mask and the ability of certain parts of the mask to allow more or
less penetration of the light energy may be a function of the
design and fabrication process. The design of the mask preferably
corresponds to the desired design of the lens in question, where
the desired index of refraction imparted in the material is
dependant on the amount of light energy the mask allows to
penetrate into the lens mold cavity. The mask may also be affected
by the light intensity.
[0079] In another embodiment of the present invention, a spatial
light modulator may be used to vary the light intensity.
[0080] Various illumination systems may be used within the scope of
the present invention. In one embodiment, a custom ultraviolet (UV)
illumination system may be used to image a planar photomask onto a
convex or concave lens surface. In the present invention, it is
preferable to have a substantially uniform light source, i.e., a
uniform intensity distribution, which is in optical connection with
a DMD. For example, if the light source is a UV bulb, a Koehler or
Abbe illumination system may be used. In another embodiment, a UV
source with a liquid light guide may be used in conjunction with a
homogenizer. In embodiments in which a laser light source is used,
the light may be collimated and thus, further homogenization of the
light may not be necessary. In another embodiment, the illumination
pattern preferably compensates for non-uniformity in the curing UV
field.
[0081] In a preferred embodiment, the lens may be cured from the
concave side of the mold. The field curvature of the illumination
system may be designed to project the desired lens design onto the
convex surface of the lens. The UV system preferably projects a
desired illumination/irradiance distribution onto a mold cavity.
Such projection may produce a radius of curvature on the order of
about 8.6 mm. Other radii may also be produced if needed.
[0082] In a preferred embodiment, energy modulation may be
accomplished using a digital mirror device (DMD). In still another
embodiment, the DMD may utilize micro-electro mechanical systems
(MEMS). In an embodiment using a DMD, the DMD software in
conjunction with a MEMS device modulates the intensity/irradiance
of the light according to an illumination scheme corresponding to
the lens design to create a spatial distribution of the needed
refractive indices. Various views of an experimental setup of this
concept are shown in FIGS. 3A, 3B, and 3C, which depict an optical
setup of the present invention. FIGS. 3A, 3B, and 3C do not include
a light source but do show a DMD 110, a plurality of lenses 120
that produce a collimated light source, and a mold 130. In some
embodiments, the plurality of lenses may not be needed. This setup
is exemplary only and may be modified or compressed for a large
scale manufacturing process, among other reasons.
[0083] As stated previously, certain parameters are necessary for a
complete lens design. These parameters are used to calculate the
proper light intensity and pattern by particular software programs
already disclosed here and their equivalents. In a preferred
embodiment, the DMD and its software control a plurality of mirrors
to on or off positions that are dependent upon the lens design.
When the light source is incident on the DMD, the computer board
associated with the DMD preferably controls the mirrors to reflect
and modulate the desired intensity/irrandiance pattern onto the
fluid ophthalmic material by switching them on or off. In another
embodiment, the computer board associated with the mirrors may
calculate and correct for distortion and other optical noise in the
system.
[0084] In this invention, specific types of modification are
preferably used to precisely transfer energy modulation into
material density modulation. Such precision results in electron
density modulation and thus the desired refractive index
modulation. These types of modification preferably involve a
suitable PVA formula, such as that described in U.S. Pat. Nos.
5,508,317; 5,583,163; 5,789,464; and 5,849,810, which are
incorporated by reference as if fully set forth herein. Other
similar prepolymers, including those used to make holographic
lenses, such as gelatin-based prepolymers, may also be used. These
materials are described in U.S. Pat. No. 5,508,317, which is
incorporated by reference as if fully set forth herein. The first
preferred material modification may comprise a material formulation
based on a PVA formulation as described in the patents listed
above, A second material formulation preferably contains refractive
index enhancing modifiers chemically attached to the hydrogel
backbone that may be substituted benzaldehydes reacted with hydroxy
groups of the PVA to cyclic acetals. The introduction of aromatic
moieties into the polymer matrix increases the overall refractive
index of the matrix, which leads to increased refractive index
differences between areas of different polymer densities.
Additional increase of refractive index differences is encouraged
by aromat/polymer interactions, which enhance the packing order of
the polymer chains in high-density areas as well as achieving
higher efficiencies. Because the modifiers are chemically bond to
the polymer matrix, the material remains biocompatible, without
requiring additional extraction steps after the lens
production.
[0085] In another preferred embodiment, a crosslinkable and/or
polymerizable fluid material is an aqueous solution of one or more
prepolymers and optionally one or more vinylic monomers, wherein
the aqueous solution includes low molecular weight additives, such
as NaCl, which exhibit a limited compatibility with a polymer
resulted from the crosslinkable and/or polymerizable fluid
material, but good compatibility with water. By virtue of the
limited compatibility, the additive causes an osmotic gradient,
which induces a contraction of a resulting polymer matrix. It is
believed that the additive separates during the hologram recording
period from areas of high irradiation intensity, in which the
polymerizing and/or crosslinking process is initiated, into areas
of low irradiation intensity. Such separation causes an osmotic
gradient, followed by localized dehydration and contraction of the
resulting polymer matrix. As a consequence, refractive index
differences between high and low irradiated areas increase and high
efficiency materials are obtained. High and low irradiated areas
are caused by the pattern of interference fringes. Because, for
example, NaCl is a component of the lens storage solution, no
extraction process is necessary during the lens preparation
process. Other additives, with similar properties may also be
added, such as HEMA or other hydrophilic monomers.
[0086] To facilitate the photocrosslinking and/or polymerizing
process, it is desirable to add a photoinitiator, which can
initiate radical crosslinking and/or polymerizing. Exemplary
photoinitators suitable for the present invention include benzoin
methyl ether, 1-hydroxycyclohexylphenyl ketone, Durocure.RTM. 1173
and Irgacur.RTM. photoinitators. Preferably, between about 0.3 and
about 5.0%, based on the total weight of the polymerizable
formulation, of a photoinitiator is used. Additionally a sensitizer
may be added to enhance the energy transer process.
[0087] In accordance with the present invention, a crosslinkable
and/or polymerizable fluid material is capable of transferring
energy modulation into material density modulation, which
subsequently results in the desired refractive index
modulation.
* * * * *
References